Decoherence in Supernova Neutrino Transformations suppressed by deleptonization

Decoherence in Supernova Neutrino Transformations suppressed by deleptonization Based on ar. Xiv: 0706. 2498 [astro-ph] Published in: Physical Review D 76: 125018, 2007. AHEP group, IFIC-Valencia. Andreu Esteban-Pretel (AHEP group, IFIC) In Andreu Esteban-Pretel collaboration with R. Tomàs, S. Pastor, G. G. Raffelt and G. Sigl.

Decoherence in SN Neutrino Transformations Suppressed by Deleptonization OUTLINE Introduction. Setup of the problem. Coherent evolution vs. decoherence. Role of the model parameters. Conclusions. Andreu Esteban-Pretel (AHEP group, IFIC) 2

Decoherence in SN Neutrino Transformations Suppressed by Deleptonization INTRODUCTION n n The crucial phenomenon Collective pair transformations require: q q n driven by atm Δm 2 and θ 13. large neutrino density a pair excess of a given flavor. SN models [Pastor and Raffelt, (2002). astro-ph/0207281] [Sawyer, (2004). hep-ph/0408265] [Fuller and Qian, (2006). astro-ph/0505240] [Duan, Fuller, Carlson and Qian, (2006). astro-ph/0606616] [Hannestad, Raffelt, Sigl and Wong, (2006). astro-ph/0608695] [Raffelt and Sigl, (2007). astro-ph/0701182] [Raffelt and Smirnov, (2007). ar. Xiv: 0705. 1830] [Fogli, Lisi, Marrone and Mirizzi (2007). ar. Xiv: 0707. 1998] [Dasgupta and Dighe (2007). ar. Xiv: 0712. 3798] [. . . ] Current-current nature of the weak interaction → (1 − cos θ) dependence for interaction energy. One would expect kinematical decoherence. - n SN context evolution similar to the single-angle case. [Duan, Fuller, Carlson and Qian, (2006). astro-ph/0606616] n Our main goal is to quantify the validity of this approximation and study the role of the different model parameters. Andreu Esteban-Pretel (AHEP group, IFIC) 3

Decoherence in SN Neutrino Transformations Suppressed by Deleptonization SETUP OF THE PROBLEM n n We work in a two-flavor scenario, νe-νx, characterized by the atmospheric Δm 2 and θ 13. Equations of motion in spherical symmetry: where: n Normalization at the ν-sphere: Andreu Esteban-Pretel (AHEP group, IFIC) 4

Decoherence in SN Neutrino Transformations Suppressed by Deleptonization COHERENT EVOLUTION VS DECOHERENCE q q q q Andreu Esteban-Pretel (AHEP group, IFIC) The flavor content decoheres quickly for both NH and IH. NH: large and abrupt decoherence far beyond rsynch. IH: at first analogous to ε = 0. 25, at some larger radius P shrinks significantly. Partial decoherence. NH: the length P also shrinks, but closely tracks Pz. IH: qualitatively equivalent to ε = 0. 06. NH: nothing visible happens, in analogy to the single-angle case. IH: similar to the single-angle case. The nutations wash out quickly. P shrinks a bit after rsynch. 5

Decoherence in SN Neutrino Transformations Suppressed by Deleptonization COHERENT EVOLUTION VS DECOHERENCE n Final location on the unit sphere of 500 antineutrino polarization vectors Andreu Esteban-Pretel (AHEP group, IFIC) n Small asymmetry (ε = 0. 12) 6

Decoherence in SN Neutrino Transformations Suppressed by Deleptonization ROLE OF MODEL PARAMETERS n Mixing angle: q q IH: multi-angle decoherence is virtually independent of sin 2θ, except for very large θ. NH: strong dependence of the critical ε on log 10(sin 2θ) Andreu Esteban-Pretel (AHEP group, IFIC) 7

Decoherence in SN Neutrino Transformations Suppressed by Deleptonization ROLE OF MODEL PARAMETERS n Effective interaction strength: Andreu Esteban-Pretel (AHEP group, IFIC) 8

Decoherence in SN Neutrino Transformations Suppressed by Deleptonization ROLE OF MODEL PARAMETERS n Vacuum oscillation frequency: q q IH: If we increase ω from 0. 3 km− 1 (our standard value) to 1 km− 1, the ε-μ-contour parallel-shifted by about 0. 035. NH: more sensitive to ω. NH Δε = 0. 035 Andreu Esteban-Pretel (AHEP group, IFIC) 9

Decoherence in SN Neutrino Transformations Suppressed by Deleptonization CONCLUSIONS n n We have explored numerically the range of parameters where different forms of evolution dominate in a realistic SN scenario. For realistic supernova deleptonization fluxes, kinematical decoherence among different angular modes likely irrelevant. n Multi-angle effects seem to be subdominant. n Good news: q q We do not have to worry about multi-angle decoherence. We can use the single-angle approximation which requires a lot less of computational time. Andreu Esteban-Pretel (AHEP group, IFIC) 10

Andreu Esteban-Pretel (AHEP group, IFIC) 11

Andreu Esteban-Pretel (AHEP group, IFIC) 12

Andreu Esteban-Pretel (AHEP group, IFIC) 13